gt ecu in a se

i was wondering if any one knew what whould happen if i were to put an ecu from a 3.4 gt version grand am in my 3.4 99 se grand am other than a higher speed limiter?

The ecu's may be the same. What is likely different is the removable EPROM inside the ECU. Normally when you replace the ECU you need to pull out the chip before you return your old one for core credit.